The spectacular proliferation of electronic devices, particularly computers, in modern society, both in numbers and complexity, demands that such devices satisfy ever increasing standards of reliability to avoid degeneration into chaos. In the early days of the computer industry, the relatively high failure rates associated with certain components diverted attention from occasional failures of other, more reliable, components. As failure rates of various electronic components have been drastically reduced, designers seeking to improve the overall reliability of a complex electronic device are forced to focus on all potential sources of failure.
One potential source of failure for an electronic device such as a computer is its cooling system. Electronic components typically generate considerable heat in a small, enclosed space. It is frequently necessary to provide auxilliary cooling of the components to prevent a rise in temperature to the point where the components are damaged or can not function normally. A common method is to provide a fan to establish an airflow past the heat producing components. If the fan should fail, the temperature of critical components may rise to the point where the component is damaged or the system shuts itself down.
In some systems, multiple fans are mounted in a bank to provide some level of redundancy in the event of failure of any single fan. In such banked designs, each fan moves a portion of the air being used to cool the device, the total cooling capacity of the bank of fans being greater than minimally necessary to cool the device. If a single fan fails, the airflow created by the remaining functioning falls is intended to be sufficient to cool the system.
In the fan bank approach, however, the loss of a single fan changes the airflow pattern. Air will continue to move past the heat generating components near the fans still operating, but airflow past those components closest to the failing fan may be considerably reduced, creating hot spots. Thus, care must be taken in fan bank designs so that any hot spots created by loss of a single fan will not exceed permissible operating temperature parameters. In addition, unless louvers are added to the fan assembly, air may go through the opening for the failing fan backwards, creating a short circuit in the airflow path which accomplishes little cooling. The design must also account for this potential backward airflow.
The existing art does not teach a simple and inexpensive redundant cooling system which maintains its cooling characteristics in the event of failure of one of the air movers.